JP2621132B2 - Aluminum piston - Google Patents
Aluminum pistonInfo
- Publication number
- JP2621132B2 JP2621132B2 JP5542485A JP5542485A JP2621132B2 JP 2621132 B2 JP2621132 B2 JP 2621132B2 JP 5542485 A JP5542485 A JP 5542485A JP 5542485 A JP5542485 A JP 5542485A JP 2621132 B2 JP2621132 B2 JP 2621132B2
- Authority
- JP
- Japan
- Prior art keywords
- piston
- casting
- less
- combustion chamber
- present
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F7/00—Casings, e.g. crankcases or frames
- F02F7/0085—Materials for constructing engines or their parts
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F3/00—Pistons
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F2200/00—Manufacturing
- F02F2200/04—Forging of engine parts
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/02—Light metals
- F05C2201/021—Aluminium
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Pistons, Piston Rings, And Cylinders (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は内燃機関におけるアルミニウム合金製ピスト
ンに関するものである。The present invention relates to an aluminum alloy piston for an internal combustion engine.
従来、小型内燃機関用のピストンにはアルミニウム合
金製のものが多く、その製造法としては重力鋳造法が一
般的であつた。しかるに従来の重力鋳造法では鋳造製品
の肉厚部に凝固収縮による引け巣を生じたり、ピンホー
ル等の欠陥があつた。しかるに近年、エンジン出力の向
上、ターボ、スーパーチヤージヤーの取りつけによるピ
ストン温度の上昇により、従来のピストンでは亀裂等の
発生する問題が生じている。Conventionally, pistons for small internal combustion engines are often made of an aluminum alloy, and a gravity casting method has been generally used as a manufacturing method thereof. However, in the conventional gravity casting method, shrinkage cavities occur due to solidification shrinkage in the thick part of the cast product, and defects such as pinholes are formed. However, in recent years, there has been a problem that cracks and the like occur in the conventional piston due to an increase in engine output and an increase in piston temperature due to attachment of a turbocharger or a supercharger.
この問題を解決する一つの手段として、鍛造ピストン
の開発が進められているが、鍛造ピストンでは製造コス
トが大巾に上昇し、かつ製造工程の関係からピストンの
熱膨脹を抑えるストラツト（支材）を設けることができ
ない。また溶湯鍛造法でも微細な組織が得られるが粗材
重量を一定にすることが困難であり、燃焼室の後加工を
必要とする等の理由で大量に使用される状態には至つて
ない。その他、ダイカスト法によつても微細な組織には
なるがエアを巻き込むためピストンのような熱処理を要
するものの鋳造には不適当である。As a means to solve this problem, forged pistons have been developed. However, forged pistons require a strut (support) that significantly increases the production cost and suppresses thermal expansion of the piston due to the manufacturing process. Cannot be provided. Further, a fine structure can be obtained by the molten metal forging method, but it is difficult to keep the weight of the coarse material constant. In addition, a fine structure is also obtained by the die casting method, but heat treatment such as a piston is required for entraining air, but it is not suitable for casting.
本発明は上記の問題点を解決し、鍛造法によらないで
製造可能な微細なアルミ組織を有する高強度アルミニウ
ムピストンを提供しようとするものである。An object of the present invention is to solve the above problems and provide a high-strength aluminum piston having a fine aluminum structure that can be manufactured without using a forging method.
本発明のアルミニウムピストンは、JIS AC8A合金か
らなり、初晶のα−Alが20μｍ以下に微細化されポロシ
ティ0.2％以下であり、かつピストンヘッドの表面に粒
径５μｍ以下のチル組織が形成されて燃焼室全体が鋳肌
のままである、竪型加圧鋳造装置を用いて製造されたこ
とを特徴とするものである。The aluminum piston of the present invention is made of a JIS AC8A alloy, the primary crystal α-Al is refined to 20 μm or less, the porosity is 0.2% or less, and a chill structure having a particle size of 5 μm or less is formed on the surface of the piston head. The entire combustion chamber is manufactured using a vertical pressure casting apparatus in which a casting surface remains as it is.
本発明ピストンに用いられるJIS AC8A合金はアルミ
ニウム−珪素系合金に属し、珪素を10ないし13％含有す
る上記合金は凝固収縮の少ないこと、溶湯の流動性の優
れていること、熱間亀裂抵抗が大きいことから、鋳造用
に適していることが特徴となつており、特にMg、Niを含
むため、引張強度やブリネル硬度等の機械的強度が高
い。Mgは熱処理によつて機械的強度を向上するために添
加される。これは熱処理によつてMg2Siが微粒として析
出するためといわれている。またFeが１％前後存在する
と型離れがよい。The JIS AC8A alloy used for the piston of the present invention belongs to an aluminum-silicon alloy, and the alloy containing 10 to 13% of silicon has low solidification shrinkage, excellent fluidity of the molten metal, and hot crack resistance. Because of its large size, it is characterized by being suitable for casting. Particularly, since it contains Mg and Ni, it has high mechanical strength such as tensile strength and Brinell hardness. Mg is added to improve mechanical strength by heat treatment. It is said that this is because Mg 2 Si precipitates as fine particles due to the heat treatment. When Fe is present at about 1%, the mold release is good.
上記のような珪素を13％程度含有するアルミニウム−
珪素系合金では鋳湯後の冷却により、通常は初晶として
珪素を晶出するはずであるが、本発明においては冷却速
度を高めることにより20μ以下のα−Alを初晶として晶
出せしめることにより組織の強度を高めている。このよ
うな組織の緻密化は、溶湯の凝固時に高圧を印加するこ
とによつてさらに高められる。Aluminum containing about 13% silicon as described above-
Silicon-based alloys should normally crystallize silicon as primary crystals by cooling after casting, but in the present invention, crystallizing α-Al of 20μ or less as primary crystals by increasing the cooling rate. Increases the strength of the tissue. Such densification of the structure is further enhanced by applying a high pressure during solidification of the molten metal.
また、本発明においては、ピストン頂部の燃焼室に相
当する部分に熱伝導性のよい材質、例えばタングステン
合金の金型を配置して水冷却することにより、金型に接
した表面を緻密で硬いチル組織としている。そして従来
の重力鋳造法による鋳肌では表面の粒子は10μｍ以上、
内部の粒子は50μｍ程度であつたものが、本発明ピスト
ンの燃焼室を形成するピストンヘツドの表面には、深さ
0.5ないし1.0mmに亘つて粒径５μｍ以下のチル組織が形
成され、従来のように表面加工を施さなくても寸法精度
の高い燃焼室が得られることになつた。なおチル組織の
粒径や深さは溶解温度、時間、鋳込温度などによつても
影響をうけ、例えば溶解温度が780℃までは高いほどチ
ル組織は深くなるが、上記温度を越えるとかえつて浅く
なる。Further, in the present invention, by disposing a mold having good thermal conductivity, for example, a tungsten alloy mold in a portion corresponding to the combustion chamber at the top of the piston and cooling with water, the surface in contact with the mold is dense and hard. It has a chill organization. And on the casting surface by the conventional gravity casting method, the surface particles are 10 μm or more,
The particles inside have a diameter of about 50 μm, but the surface of the piston head forming the combustion chamber of the piston of the present invention has a depth of
A chill structure having a particle size of 5 μm or less was formed over 0.5 to 1.0 mm, and a combustion chamber with high dimensional accuracy could be obtained without performing surface processing as in the prior art. Note that the grain size and depth of the chill structure are also affected by the melting temperature, time, casting temperature, and the like.For example, the higher the melting temperature is up to 780 ° C, the deeper the chill structure becomes. And shallower.
このように組織が緻密で比重が高く、かつ燃焼室全体
が鋳肌のままである本発明のアルミニウムピストンは、
溶湯を静かにかつ連続的に供給し得てガスを巻き込まな
い竪型加圧鋳造装置を使用して製造される。As described above, the aluminum piston of the present invention having a dense structure and a high specific gravity, and the entire combustion chamber remains cast surface,
It is manufactured using a vertical pressure casting apparatus that can supply the molten metal quietly and continuously and does not involve gas.
以下、本発明の実施例を図面に従つて説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
JIS AC8A合金を760℃にて融解し、竪型加圧鋳造装置
を用いて、150℃に予熱したピストン鋳造用金型内に500
Kg/cm2の圧力下に１ないし２秒で充填した。The JIS AC8A alloy was melted at 760 ° C and placed in a piston casting mold preheated to 150 ° C using a vertical pressure casting machine.
Filling was performed in 1 to 2 seconds under a pressure of Kg / cm 2 .
上記金型を水冷等により60℃に冷却すると20μｍ以下
のα−Alが初晶として晶出し始めるので、このとき、即
ち充填後２ないし８秒後に肉厚部に対して1500Kg/cm2の
局部加圧を印加する。When the mold is cooled to 60 ° C. by water cooling or the like, α-Al of 20 μm or less starts to crystallize as primary crystals. At this time, that is, 2 to 8 seconds after filling, a local portion of 1500 kg / cm 2 with respect to the thick portion is formed. Apply pressure.
第１図はピストンの断面図を表わし、１はピストンヘ
ツド、２は燃焼室、３は肉厚部、４はスカート、５はピ
ン孔回りを示す。凝固期間中の肉厚部３に対して矢印方
向に加圧すると、一般の重力鋳造法で生ずるエアギヤツ
プがなくなるので絶えず金型と接触し、冷却速度が早く
なり、15μｍ以下の微粒子からなる組織が形成される。
そこで既に凝固して樹枝状晶となつている部分に溶湯が
圧入されるので引け巣がなくなりポロシテイが減少す
る。以上が加圧下における凝固現象の特徴であり、本実
施例のように直径80mmのピストンで肉厚部の厚さが30mm
の場合には加圧保持時間は５秒である。FIG. 1 is a sectional view of a piston, in which 1 is a piston head, 2 is a combustion chamber, 3 is a thick portion, 4 is a skirt, and 5 is a pin hole area. When pressure is applied to the thick portion 3 during the solidification period in the direction of the arrow, the air gap generated by the general gravity casting method is eliminated, so that the contact is constantly made with the mold, the cooling speed is increased, and the structure composed of fine particles of 15 μm or less is formed. It is formed.
Then, the molten metal is injected into the portion where the solidification has already been made into dendrites, so that shrinkage cavities are eliminated and porosity is reduced. The above is the feature of the solidification phenomenon under pressure, and the thickness of the thick part is 30 mm with a piston having a diameter of 80 mm as in this embodiment.
In this case, the pressure holding time is 5 seconds.
本発明ピストンの第二の特徴として鋳肌のままの燃焼
室２を有していることが挙げられるが、かかる燃焼室２
を形成するには、熱伝導率の高いタングステン合金を材
質とする金型を使用し、さらに水冷却等により金型温度
を70℃以下に冷却してピストンヘツド１の表面に粒径５
μｍ以下、ポロシテイ0.01％以下のチル組織６を形成せ
しめた。また本実施例ではピン孔回り５を鋳抜いてある
ので軽量化され、さらにスカート４の肉厚が従来の金型
鋳造法によるものよりも0.5mm薄くしてあるので、約15
％の軽量化となつた。このような鋳肌のままの燃焼室を
有し、かつ軽量化されたピストンを得るためには竪型加
圧鋳造装置が使用される。すなわち第２図に示す溶湯鍛
造法では注湯量の変動によつてピストンヘツド１の厚み
（ｈ）にバラツキが生じ後加工を必要とするに対し、第
３図の竪型加圧鋳造装置によればビスケツト７の高さ
（Ｌ）の調整により、厚み（ｈ）が一定となり鋳肌のま
まの燃焼室を得ることができる。A second feature of the piston of the present invention is that it has a combustion chamber 2 with a cast surface as it is.
Is formed by using a mold made of a tungsten alloy having a high thermal conductivity, and further cooling the mold temperature to 70 ° C. or less by water cooling or the like, and forming a particle size of 5 on the surface of the piston head 1.
A chill structure 6 having a size of not more than μm and a porosity of not more than 0.01% was formed. Further, in this embodiment, the area around the pin hole 5 is cast out, so that the weight is reduced. Further, since the thickness of the skirt 4 is 0.5 mm thinner than that of the conventional mold casting method, about 15 mm is obtained.
% Reduction in weight. In order to obtain a lightweight piston having a combustion chamber with such a casting surface, a vertical pressure casting apparatus is used. That is, in the melt forging method shown in FIG. 2, the thickness (h) of the piston head 1 varies due to a change in the pouring amount, and post-processing is required. On the other hand, the vertical pressure casting apparatus shown in FIG. For example, by adjusting the height (L) of the biscuit 7, the thickness (h) becomes constant and a combustion chamber with a cast surface can be obtained.
かくして１サイクル約１分で得られるピストンの鋳肌
は従来の重力鋳造法によつて得られる鋳肌よりも組織が
緻密であり、内部の組織も表面程ではないが従来よりも
微細となつている。そこで熱処理（T7）後切り出したテ
ストピースの引張強度は32Kg/cm2であつた。そして従来
の方法によつて得たピストンの同一部位から切り出した
テストピースについても測定し、疲労強度とともに第４
図のグラフに図示すると、いずれも約50％の増加となつ
ていることが判る。Thus, the casting surface of the piston obtained in about one minute per cycle has a finer structure than the casting surface obtained by the conventional gravity casting method, and the internal structure is not as good as the surface but is finer than the conventional one. I have. Therefore, the tensile strength of the test piece cut out after the heat treatment (T 7 ) was 32 kg / cm 2 . Then, a test piece cut from the same part of the piston obtained by the conventional method was also measured, and together with the fatigue strength, the fourth piece was obtained.
As shown in the graphs in the figure, it can be seen that each of them increases by about 50%.
次に本発明ピストンと重力鋳造法によるピストンとを
６気筒3000ccの実験用エンジンに装着し、6000r.p.mで
運転したところ従来のピストンでは60時間で亀裂を発生
したのに対し、本発明ピストンでは200時間後でも異常
がなかつた。Next, the piston of the present invention and the piston by gravity casting were mounted on a 6-cylinder 3000 cc experimental engine and operated at 6000 rpm, whereas the conventional piston cracked in 60 hours, whereas the piston of the present invention No abnormality was found even after 200 hours.
上記の如く本発明ピストンは冷却速度の調節、局部加
圧の適用によつて全体の組織が緻密となり、金型材料の
選択によつてピストンヘツドにチル組織が形成されてい
る。さらに竪型加圧鋳造装置の使用によつて溶湯の充填
が静かに連続的に行なわれるのでガスの巻き込みを防止
することができるほか、溶湯量を調節できるので、上記
チル組織の効果と相俟つて鋳肌のままで寸法精度の高い
燃焼室を得ることができ、製造コスト低減の効果が大き
い。As described above, the entire structure of the piston of the present invention is made fine by adjusting the cooling rate and applying local pressure, and a chill structure is formed on the piston head by selecting a mold material. In addition, the use of the vertical pressure casting apparatus allows the molten metal to be filled quietly and continuously, thereby preventing gas entrainment. In addition, since the amount of molten metal can be adjusted, the effect of the chill structure can be obtained. As a result, a combustion chamber with high dimensional accuracy can be obtained without changing the casting surface, and the effect of reducing the manufacturing cost is great.
第１図は本発明ピストンの断面図を表わし、 第２図は溶湯鍛造法によるピストンヘツドの模式断面図
を表わし、 第３図は竪型加圧鋳造によるピストンヘツドの模式断面
図を表わし、 第４図はピストンの引張強度、疲労強度のグラフを表わ
す。 図中、 １……ピストンヘツド、２……燃焼室 ３……肉厚部、４……スカート ５……ピン孔回り、６……チル組織 ７……ビスケツトFIG. 1 is a cross-sectional view of the piston of the present invention, FIG. 2 is a schematic cross-sectional view of a piston head formed by a molten metal forging method, FIG. FIG. 4 shows a graph of the tensile strength and fatigue strength of the piston. In the drawing, 1 ... piston head, 2 ... combustion chamber 3 ... thick part, 4 ... skirt 5 ... pin hole circumference, 6 ... chill structure 7 ... biscuit
───────────────────────────────────────────────────── フロントページの続き (72)発明者 四日 淳一 豊田市トヨタ町１番地 トヨタ自動車株 式会社内 (56)参考文献 特開 昭59−108849（ＪＰ，Ａ) 特開 昭57−500187（ＪＰ，Ａ) 特開 昭61−215860（ＪＰ，Ａ) 軽金属，Ｖｏｌ．33〔Ｎｏ．７〕 （1983）軽金属学会Ｐ．392−398 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Junichi Yokkaichi 1 Toyota Town, Toyota City Inside Toyota Motor Corporation (56) References JP-A-59-108849 (JP, A) JP-A-57-500187 ( JP, A) JP-A-61-215860 (JP, A) Light metal, Vol. 33 [No. 7] (1983) Light Metal Society of Japan. 392-398
Claims (1)
0μｍ以下に微細化されポロシティ0.2％以下であり、か
つピストンヘッドの表面に粒径５μｍ以下のチル組織が
形成されて燃焼室全体が鋳肌のままである、竪型加圧鋳
造装置を用いて製造されたことを特徴とするアルミニウ
ムピストン。(1) It is made of JIS AC8A alloy, and α-Al of primary crystal is 2
Using a vertical type pressure casting device, which is refined to 0 μm or less and has a porosity of 0.2% or less, and a chill structure having a particle size of 5 μm or less is formed on the surface of the piston head and the entire combustion chamber remains a casting surface. An aluminum piston characterized by being manufactured.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5542485A JP2621132B2 (en) | 1985-03-19 | 1985-03-19 | Aluminum piston |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5542485A JP2621132B2 (en) | 1985-03-19 | 1985-03-19 | Aluminum piston |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61212655A JPS61212655A (en) | 1986-09-20 |
| JP2621132B2 true JP2621132B2 (en) | 1997-06-18 |
Family
ID=12998194
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5542485A Expired - Lifetime JP2621132B2 (en) | 1985-03-19 | 1985-03-19 | Aluminum piston |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2621132B2 (en) |
-
1985
- 1985-03-19 JP JP5542485A patent/JP2621132B2/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| 軽金属，Ｖｏｌ．３３〔Ｎｏ．７〕（１９８３）軽金属学会Ｐ．３９２−３９８ |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61212655A (en) | 1986-09-20 |
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